WASHINGTON — A trial set for Sunday in Egypt of at least 16 Americans could have far-reaching implications for the pro-democracy movement that has been sweeping the Middle East.

Barring some last-minute flourish of face-saving diplomacy, it also could mean a setback to the U.S. government's efforts since the Cold War to combat authoritarian regimes and to promote human rights.

The Americans are employees of four U.S.-based non-governmental organizations, known as NGOs. They have been assisting Egyptian groups with election reforms, voter education and other civil society programs.

But they have been charged with operating without government approval and interfering in local politics, along with more than two dozen others from Egypt, Jordan, the Palestinian territories and Germany. The charges could lead to prison sentences of five years.

"It can have a chilling effect on the way NGOs, which are already under pressure in a lot of these countries, operate," said Charles Dunne, director for Middle East and North Africa programs for Freedom House, a human rights and democracy advocacy group, and among the NGOs that Egyptian authorities raided in December and seized files.

Already in Bahrain, a top military leader in the small Persian Gulf kingdom has accused 22 mostly U.S-based NGOs of plotting against the government. Home to the U.S. Navy's 5th Fleet, Bahrain, like Egypt, is a key Middle East ally.

The others NGOs facing charges in Egypt are the National Democratic Institute, the International Republican Institute and the International Center for Journalists. A fifth, the Konrad Adenauer Foundation, is based in Germany.

Dunne was among the Americans ordered to appear in court, but he remains in the U.S. and has no intention of showing up.

A former diplomat who served in Cairo and elsewhere in the region, he said, "If Egypt is able to repress these NGOs, that's going to embolden them and other governments in the region to do more of the same."

The number of international NGOs has ballooned over the past two decades, from 6,000 in 1990 to more than 50,000 in 2006, according to the Yearbook of International Organizations.

The National Democratic Institute and the International Republican Institute grew out of a speech that President Ronald Reagan gave to the British Parliament in 1982.

He called for "a crusade for freedom" that would "move toward a world in which all people are at last free to determine their own destiny."

Congress created the two party-based NGOs a year later to promote human rights and democracy abroad. Both operate programs in dozens of nations around the globe and were working on voter education and government oversight projects in Egypt.

They are politically well connected, with current and former members of Congress and government sitting on their respective boards. But Kenneth Wollack, president of the National Democratic Institute, said their work abroad is nonpartisan.

"We support a process, not ideologies," he said. "We don't go in and choose winners."

Officials with the International Republican Institute declined to comment because of the pending trial.

The bulk of both organizations' money comes from tax dollars. The Democratic NGO received $120 million from the U.S. government last year; the Republican NGO, $75 million.

Most NGOs rely largely on private donations. Several officials whose groups also receive government support, to one degree or another, said they are not arms of the State Department carrying out the official aims of U.S. foreign policy. But they said their work serves the national interest.

"We represent a convergence of the strategic and moral interests of the United States," Wollack said.

Sam Worthington, president and CEO of InterAction, an alliance of nearly 200 American NGOs that works around the world, said they are independent but try to align with American foreign policy "when we can."

He said the core mission for many NGOs is promoting civil society, which he described as "a more accountable society focused on the well-being of its citizens."

They can be as big and far reaching in their pursuits as well-known organizations like Habitat for Humanity and CARE, or small, volunteer groups that organize to help around natural disasters, like the Haiti earthquake two years ago.

They help set up community food kitchens, educational programs and health services. Others, in their promotion of democracy, demand government transparency and help set up and monitor free elections.

The International Foundation for Electoral Systems has been working on election reform in Egypt since 2006, six years before the Arab Spring.

"There are brave people both within the society and outside who are trying to make the voice of the people heard through the ballot box," said Bill Sweeney, the foundation's president and CEO. "This action in Egypt might deter people from trying to express themselves and seek greater freedom."